The present invention relates to a process for detecting foreign particle and scratch defects on semiconductor products processed through a semiconductor manufacturing processing tool.
In semiconductor manufacturing, contamination, for example by particles or foreign substances, and scratches constitutes a great risk with the consequences of reducing the quality and total failure of the electronic components. For this reason, the environmental conditions during semiconductor fabrication are kept at the highest possible quality level by filters and by monitoring the physical conditions in the room. That is, the number of contaminating particles per volume element is kept as low as possible.
In order to meet the requirements on structure widths which decrease to an ever increasing extent, much better clean conditions, as compared with the clean room condition, are created by using mini environments to transport the semiconductor products (for example, semiconductor wafers, masks or flat panel displays) to and from the manufacturing tools. As compared with the surrounding clean room, the air in the mini environments has a much lower number of contaminating particles per volume. The mini environments may also be called wafer carriers, substrate transports or substrate transfer carriers, hereafter collectively referred to as wafer carriers.
Unfortunately, all moveable parts and components produce contamination, even during fault-free operation. The handling systems of the manufacturing tools for semiconductor products can produce unacceptable contamination if maladjustments of the handling systems arise, for example, when semiconductor products being loaded or unloaded in a wafer carrier are scraped as a result of an inaccurate adjustment; in the process, layers on the semiconductor product or in/on the wafer carrier flake off and become a contamination source. The particles flaked off can be deposited on the same semiconductor product or on the semiconductor products which follow or are located underneath and can lead to yield losses in the latter.
In particular, wafer carriers may themselves constitute a serious contamination source. Typically, such wafer carriers are used during the deposition of layers on semiconductor products. Therefore, not only are the semiconductor products but also the wafer carriers may be coated with the material respectively deposited.
Since the wafer carriers may be neither cleaned immediately nor replaced following processing of semiconductor products in a manufacturing tool, contaminants may accumulate in the course of processing semiconductor products through several tools. Accordingly, foreign particle defects due to contamination in the manufacturing tools or the wafer carriers may remain undetected for an undesirably long time.